Objective Oppositional defiant disorder (ODD) is a behavioral disorder whose most important traits are constant negative repetitious behavior pattern, pertinacity, disobedience, and hostility against power symbols. It results in significant clinical disorders in educational, social, and occupational functions. Moreover, parents of children with ODD employ strict punitive methods against their behavioral problems, which worsens the children’s behavioral problems. As a result, parents have a hard time managing their children. The aim of the present study was to investigate the effect of parental behavioral education on mothers of children with ODD.Materials & Methods The research design was quasi-experimental with a pretest posttest and control group. The study population consisted of all mothers of children between 9 to 11 years from the city of Azna. Thirty mothers of children with ODD whose scores in the subscales of coping behaviors and aggressive behavior in Child Behavior Checklist were above the questionnaire cut-off point score were selected via at-hand sampling after homogenizing them in variables such as education, gender, severity of symptoms, age and maternal education. They were randomly paired and assigned into experimental and control groups after obtaining consent from the mothers . The inclusion criteria for the participants of this study were as follows: high aggression in children with the cut-off score in accordance with the Child Behavior Checklist. The age of the mothers was another inclusion criterion. All the mothers were between 33 to 37 years old. In this study, all of them were from two-parent families. The number of children with ODD was also considered for households having a child with ODD. Children’s age was another inclusion criterion in this study. All children between 9-11 years of age were included in the study. Mothers’ education level was also considered, with those included in the sample being diploma-educated. The research tools included the Child Behavior Checklist for parents (1991) and Child Symptom Inventory Parents’ form (1997). Parent’s behavioral training was accomplished across nine 90-minute sessions for the experimental group. In the end, the two groups completed the questionnaires. Analysis of covariance was used to analyze the data.Results The results showed that the effectiveness of behavior management training among mothers with ODD children with regard to reducing their symptoms was more in the experimental group compared with that in the control group (P<0.001). The parents’ behavior training also reduced aggressive behaviors in the experimental group (P<0.012).Conclusion Overall, the findings suggest that mothers' behavioral training reduces the symptoms of ODD in children and prevents inappropriate behavior in family environment. Learning and applying principles such as avoiding punishment along with distinction between discipline and punishment, are the main principles of the training program that can reduce behavioral problems in children and increase their desirable behaviors.